class Dog {
    //构造函数
    constructor(name, age) {
        console.log('构造函数执行了', this);
        this.name = name;
        this.age = age;
    }
    bark() {
        console.log('wangwangwang');
    }
}
const dog = new Dog('xiaohei', 4);
console.log('dog', dog);
